[SFML/C++] Linking shader returns GL_FALSE, but no log, and no output on screen

Hello
So I'm follow this: ogldev.atspace.co.uk/www/tutorial04/tutorial04.html tutorial in order to learn OpenGL. And currently I'm learning to use shaders, however, when I'm linking my shader program, "glGetProgramiv" returns GL_FALSE but there's no error log from "glGetProgramInfoLog".

I'm currently programming on Xubuntu (Ubuntu 12.10), and using the "NVIDIA binary Xorg driver, kernel module and VDPAU library from nvidia-current (proprietary, tested)" driver. On a Geforce GTX 560 Ti if that matters. But anyway, below is a link to my code, the first page is my main.cpp file where I run the rendering and gameloop, and in the symGL file i have a little utility class for loading shaders. Any idea what's the problem?

Code: gist.github.com/4592760
Output: i.imgur.com/QNE67JX.png

Source code of the vertex shader can be found in the output image as well.